The invention pertains to the purification of power plant condensate water. In nuclear power plants and in conventional fossil fuel plants, it is desired to maintain the level of dissolved and suspended species in the steam loop at a minimum to avoid corrosion. In a boiling water nuclear reactor (BWR), it is especially desirable to maintain the water in the steam loop as pure as possible because the impurities in that loop are subjected to irradiation when passing through the "hot" side of the loop. This causes such impurities in many cases to themselves become radioactive species, which must then be handled and ultimately disposed of in a safe manner when it is necessary to clean the steam loop. Furthermore, accumulation of suspended solids may cause pressure build up in the system, reducing flow rate and lessening the efficiency of the power plant operation. Consequently, the lower the level of impurities, especially suspended solids, that can be maintained in the steam loop the better.
Japanese Kokai publication 1-174998 (1989) proposes the removal of suspended impurities from the primary coolant of a boiling water nuclear power reactor by use of mixed bed ion exchange resins having low cross-linker (divinylbenzene) content of 3-7.5 percent. The publication theorizes that lower cross-linked resins have larger micropores and are relatively soft and more elastic than ion exchange resins having a higher level of cross-linkage and that these properties permit the lower cross-linked resins to more effectively remove the "crud" from condensate water.
In Japanese Kokai publication 63-59355 (1988) it is noted from an English abstract of same that a cation exchange resin was oxidized in a dilute sodium sulfate solution using platinum electrodes with a 2 ampere current for 3 to 4 hours. The oxidized resin is said to be useful for removal of fine, amorphous particles in condensate water, which particles are produced from corrosion of the piping and other materials of construction in thermal or nuclear power plants.
In U.S. Pat. No. 4,564,644 are described shell/core morphology ion exchange resins. They are of the same structure as those utilized in the present process. They are said at column 13, lines 3-12, to be useful under harsher conditions than prior gel-type resins and in particular for condensate polishing and in mining operations. However, their special ability to remove colloidal iron to a previously unattainable degree is not suggested nor is any special utility for BWR condensate crud removal mentioned.